The present invention relates to intraocular lenses, and in particular to intraocular lenses for placement in the anterior or posterior chamber of an eye following removal of the natural lens.
In several designs of intraocular lenses that are described in issued U.S. patents, the legs for centering the lens body work through tangential contact between a portion of the leg and the tissue of the eye. For instance, in some posterior chamber lenses, a portion of each leg tangentially contacts the ciliary body, which is the cleft at the intersection of the iris and the posterior capsule. In some anterior lenses, a portion of each leg tangentially contacts the junction between the cornea and the iris. For purposes of this invention, contact is considered "tangential" so long as the leg portion in question has the same geometrical slope as the tissues in contact with the leg portion. Thus, tangential contact within this definition is considered to include not only contact at one point, but also contact along a substantial length of the eye tissue where the curvature of the leg corresponds very closely to the curvature of the tissue. Lenses of this type having filamentary legs are described in U.S. Pat. No. 4,477,931 to Kelman, U.S. Pat. No. 4,468,820 to Uhler, et al., U.S. Pat. No. 4,435,855 to Pannu, U.S. Pat. No. 4,418,431 to Feaster, and U.S. Pat. No. 4,159,546 to Shearing. Lenses of this type having legs which are non-filamentary, i.e. comprising a pair of tabs or equivalent means, are described in U.S. Pat. No. 4,414,694 to Choyce, for example.
Leg means of this type necessarily exert some force against the eye tissues in order to hold the lens in position. The force is alleviated somewhat by various configurations of the leg, between the region which contacts the eye tissues and the point at which the leg is attached to the lens body, or by providing that the leg can lie in a plane which is parallel to and/or offset from the plane of the lens body. However, since there must still be force applied to the eye tissues, which can provide discomfort and/or trauma to the tissues, it is desirable to provide further relief.
Another problem encountered in this field is that lenses made entirely of clear material are difficult to work with because they are difficult for the practitioner to see before, during and after implantation in the eye. Thus, there is a need for a lens which has colored leg means, without having to mold colored legs separately and then attach them in some manner to the lens body.